This paper describes a chiral phosphoric acid-catalyzed sulfamination of amino-alkenes to form optically active 2-substituted pyrrolidines and piperidines in up to 86% ee.
Determining the influence scope of the airflow disorder is an important problem after coal and gas outburst accidents in ventilation systems. This paper puts forward the indexes of airflow disorder, ...including the length of the excavation roadway, the outburst pressure, the pressure difference of the air door, and the air quantity of the auxiliary fan. Using the orthogonal table of L9 (34) and numerical simulation method, the characteristics of airflow reversal are studied, and the outburst airflow reversal degree is calculated should the ventilation facility fail. Furthermore, on the basis of fuzzy comprehensive optimization theory, the comprehensive evaluation model of the airflow disorder is established. The results show that the length of the excavation roadway is the most important factor affecting the stability of the ventilation system, followed by the outburst pressure, pressure difference of the air door, and air quantity of the auxiliary fan. The influence of a gas outburst accident on the return air system is greater than that on the inlet air system, and a larger air velocity has a greater impact on the ventilation system, especially the air inlet part. Moreover, the airflow reversal degree of the ventilation system increases with the increase of the outburst pressure or decreases with the length of the excavation roadway. This paper provides a basis for the prevention of gas outburst accidents.
Carbon dots (CDs) have photoconversion performance and have a wide range of applications in agriculture. However, the solution of CDs is susceptible to quench under evaporation of sunlight and is ...easy to run-off when influenced by the external environment. Here, PVA-coated CDs were used to overcome the solid-state quenching and to prepare CDs microcapsules-polyurethane Film for plant cultivation. In this work, CDs microcapsules which can convert ultraviolet light into blue light for plant growth, were prepared by the “water/oil/water” method, and light-converting CDs microcapsules polyurethane film (CMPF) was prepared by doping CDs microcapsules with polyurethane. The study showed that polyurethane film has good mechanical properties and self-healing ability, the CMPF was able to effectively promote the growth of lettuce, and the effect was most significant at the CDs microcapsules concentration of 4000 mg/L. Compared with the blank group, the fresh and dry weights were increased by 177 % and 143.5 %, respectively, and the content of chlorophyll a, chlorophyll b, carotenoids, and soluble protein were increased by 14.5 %, 188.5 %, 43.3 %, and 17.9 %, respectively. Application of CDs to modulate plant lighting growth regulators for efficient use of ultraviolet (UV) light.
The mining technology of gob-side entry retaining without a coal pillar is gradually becoming a mature and increasingly important mining technology. As it maintains the roadway near goaf, the air ...leakage should be greater than a U-type ventilation system in goaf, so it is prone to cause coal spontaneous combustion problems. CO2 is an inert gas, and it is usually used to prevent spontaneous combustion and extinguish coal fire. However, there is a lack of research on characteristics and safety of CO2 for the mining technology of gob-side entry retaining without the coal pillar. In this paper, the indexes of influencing factors were proposed on gas, pipelines, and mining technical parameters. Using a three-dimensional physical model of coal stope, the gas migration law of CO2, the relationship between gas injection rate and the oxidation zone area, and the safety of the CO2 inerting technology were analyzed. The results indicate that the O2 concentration is diluted between the working face and the injection port, especially in the air intake side. Furthermore, the CO2 injection rate is an important parameter to the fire prevention and extinguishing technology. When the gas injection rate ranges from 240 to 720 m3/h, the oxidation zone area varies from 7380 to 14 760 m2, and the gas injection rate grows exponentially with the area of the oxidation zone. Moreover, the redundant CO2 gas flows to the retaining roadway, and it reduces the O2 concentration, resulting in asphyxia accidents of miners. The research results are helpful to balance the relationship between inert gas injection and production safety and provide guidance for the practical application of the inert gas fire prevention technology.
A simplified pulse decay method (PDM) with only a single downstream reservoir is proposed to replicate the in situ conditions for reservoir fluid flow, where the pore pressure at any location ...declines as production continues. The proposed PDM also allows determining the effective porosity and permeability for the core sample under replicated in situ conditions. A mathematical model is firstly established to closely represent the experimental design and verify the feasibility of the method. The analytical solutions of the model are derived to calculate the effective sample porosity and permeability. A series of experiments are then conducted under triaxial stress condition, and a detailed comparison is also made between the PDMs with a single upstream reservoir and a single downstream reservoir. The experimental results showed that accurate measurements on effective sample porosity and permeability can be achieved by the single downstream reservoir PDM due to its capability of better replicating the in situ fluid flow behavior, which extends the application of the transient technique. It is also found that the pore pressure along the sample changes linearly, and its gradient varies with time, indicating the applicability of the single‐reservoir PDMs in permeability determination. This method also lays a foundation for studying flow behavior when a second fluid phase evolves during pressure decline, which occurs in many reservoirs.
A simplified transient technique is proposed to simultaneously measure porosity and permeability of tight gas formations, and the influence of gas compressibility, gas compressive storage, and gas sorption on the measured permeability is investigated experimentally and numerically.
Mode-division multiplexing (MDM) can achieve ultra-high data capacity in optical fiber communication. Several impressive works on multicore fiber (MCF), multi-mode fiber, and few-mode multicore fiber ...have made significant achievements in MDM. However, none of the previous works can simultaneously maintain the transmission loss, chromatic dispersion (CD), and differential group delay (DGD) at a relatively low level. A nested multiple hollow-core anti-resonant fiber (NMH-ARF) has significant potential for applications in MDM. This study proposes a novel NMH-ARF with its structural design based on the traditional single-core nested anti-resonant fiber. We increased the number of nodes between capillaries. By changing the position of the nested tubes, several interconnected areas form when a single core is separated. We investigated the mode-coupling theory and transmission characteristics of this fiber. This fiber structure showed a low sensitivity to bending and achieved a super-low DGD and a super-low confinement loss (CL) at a wavelength of 1.55 µm while keeping CD relatively low.
An efficient enantioselective bromoaminocyclization of 2-benzofuranylmethyl N-tosylcarbamates catalyzed by a chiral phosphine oxide–Sc(OTf)3 complex is described. A wide variety of optically active ...spiro benzofuran oxazolidinones can be obtained with high enantioselectivities.
This study aimed to evaluate the association between preoperative hs-cTnI and long-term mortality and major adverse cardiovascular events (MACE) in colorectal cancer patients.
This single-center ...retrospective cohort study included 1105 consecutive colorectal cancer patients who received tumor resection surgery between January 2018 and June 2020. Inclusion criteria were an age ≥ 18 years and had been tested for hs-cTnI on admission within 7 days prior to tumor resection surgery. Exclusion criteria were emergent surgery, failure to received tumor resection surgery, hospital death, there was clinical evidence of unstable coronary artery disease or pulmonary embolism occurred before operation according to medical record. The primary endpoint was all-cause death. Secondary endpoint was major adverse cardiovascular events (MACE).
A total of 1105 patients were enrolled: 1032 with normal hs-cTnI and 73 with elevated hs-cTnI. The mean follow-up was 24.4 ± 10.8 months, 176 patients died and 39 patients met MACE. In the elevated troponin group, 50%, 32.1% and 17.9% died from cancer, cardiovascular and other causes, while those in the normal troponin group were 75.7%, 2% and 22.3%, there was statistical difference between 2 groups (P < 0.001). Patients with elevated preoperative hs-cTnI had significantly higher mortality (P < 0.001) and more MACE (P < 0.001) compared with those with normal hs-cTnI. A propensity-matching analysis were performed, resulting in 151 patients with normal hs-cTnI and 60 patients with elevated hs-cTnI. The matched population had the similar results for all-cause death (P = 0.009) and MACE (P = 0.001). The results were consistent after further excluding 147 patients who had received chemoradiotherapy prior to surgery in subgroup analysis. The results of multivariate Cox regression analysis shown that hs-cTnI was one of the best predictors for all-cause death (hazard ratio HR 2.278; 95% confidence interval CI 1.19-4.361) and MACE (HR, 3.523; 95%CI, 1.477-8.403) in total populations, similar results were found in subgroup analysis.
Colorectal cancer patients without myocardial ischemia manifestation but with elevated hs-cTnI prior to tumor resection surgery were at increased risk for long-term all-cause death and MACE, irrespective of whether they have received chemoradiotherapy prior to surgery.
Supramolecular polymer networks (SPNs), crosslinked by noncovalent bonds, have emerged as reorganizable and recyclable polymeric materials with unique functionality. However, poor stability is an ...imperative challenge faced by SPNs, because SPNs are susceptible to heat, water, and/or solvents due to the dynamic and reversible nature of noncovalent bonds. Herein, the design of a noncovalent cooperative network (NCoN) to simultaneously stabilize and reinforce SPNs is reported, resulting in an ultrastable, superrobust, and recyclable SPN. The NCoN is constructed by multiplying the H‐bonding sites and tuning the conformation/geometry of the H‐bonding segment to optimize the multivalence cooperativity of H‐bonds. The rationally designed H‐bonding segment with high conformational compliance favors the formation of tightly packed H‐bond arrays comprising higher‐density and stronger H‐bonds. Consequently, the H‐bonded crosslinks in the NCoN display a covalent crosslinking effect but retain on‐demand dynamics and reversibility. The resultant ultrastable SPN not only displays remarkable resistance to heat up to 120 °C, water soaking, and a broad spectrum of solvents, but also possesses a superhigh true stress at break (1.1 GPa) and an ultrahigh toughness (406 MJ m−3). Despite the covalent‐network‐like stability, the SPN is recyclable through activating its reversibility in a high‐polarity solvent heated to a threshold temperature.
The design of a noncovalent cooperative network (NCoN) to strengthen and stabilize the supramolecular polymer network is reported. The superb multivalence cooperation makes the hydrogen‐bonded crosslinks in the NCoN display a covalent crosslinking effect, resulting in a superroubst and recyclable supramolecular polymer network with remarkably high resistance to heat up to 120 °C, water soaking, and H‐bond‐destructive solvents.
Highly sensitive triethylamine (TEA) gas sensors have undergone extensive research, yet slow response/recovery speed, poor moisture resistance, and high detection limitation limited their further ...application. Herein, pure SnO2 and Co-doped SnO2 nanofibers have been synthesized by a simple electrostatic spinning technique, and their sensing performance has been systematically analyzed. As a result, the sensors based on the 2 mol% Co-doped SnO2 nanofibers show a good response (Ra/Rg = 50.2) to 100 ppm TEA at 200 °C. In addition, the 2 mol% Co-doped SnO2 based sensors display a rapid response and recovery speed, low limit of detection, superior anti-humidity property, and excellent reproducibility for TEA. The improved sensing performance owing to enhanced chemisorbed oxygen as a consequence of the Fermi level regulation and the abundant oxygen vacancies. All in all, 2 mol% Co-doped SnO2 nanofibers have the potential for efficient detection of low concentrations of TEA.
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•Porous 2 mol% Co-SnO2 nanofibers were synthesized by an electrospinning method.•The regulation of the energy level of SnO2 for the efficient detection of TEA.•Co doping significantly increased the oxygen vacancies of SnO2 nanofibers.•The doping of Co could enhance the sensing performance of SnO2 for TEA.
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